Having been invited to comment by blog-owner Kate, I'll make a couple of observations of my own.
Rats are part of the natural world, the world in which we live too. But, as ever, we make judgements about how other life forms impinge on our personal environment; if they reach pest proportions they are a pest. This might be different for different people. A farmer, who rightly recognizes the damage they do and the danger of disease they present, might regard one rat as a pest. Others, who see rats as little more than big mice, might tolerate them more.
I use to have rats, I experimented on them at university. There were six of them housed in a small outbuilding run by the animal behaviour group. They all had names, were all tame and friendly, and all squeaked loudly in recognition when I went to visit them. I made them hungry for 24 hours and watched the ratio of seconds spent feeding or drinking when they were then offered full food and water again. A few days later I made them thirsty for 24 hours. I can't quite remember what the experiment showed, but it was all good fun. The other student who did the same project went on to keep her rats as pets. I did not have room in my small flat.
I think rats are fascinating creatures, but would have the same compunction to bashing a rat's brains out with a shovel, as I would to swatting a housefly.
I have rats breeding in my compost bins at the moment. So I have stopped adding anything. Instead, all garden and kitchen waste goes off to the local recycling centre for them to compost in industrial units. I will start again in spring. I know why I have rats in my garden, and I'm doing something about it. What I find hart to take is the surprise that some people have when they realize there are rats about, but continue to scatter food for birds and foxes. We must all take responsibility for what we do in the environment, and adjust our behaviour if the results offend us.